The typical process to establish oil and gas production forecasts includes the construction of 3D subsurface models and flow simulation using such models as an input.
Subsurface models may comprise, for example, reservoir flow, basin, and geo-mechanical models. These comprise gridded 3D representations of the subsurface used as inputs to a simulator allowing the prediction and real time monitoring of a range of physical properties as a function of controlled or un-controlled boundary conditions:
Reservoir flow models aim to predict fluid flow properties, primarily multi-phase rates (and composition), pressure and temperature, under oil and gas field or aquifer development scenarios.
Basin models aim to predict over time the types of hydrocarbon being generated out of kerogen, and the location of hydrocarbon trapping at geological timescales.
Geo-mechanical models aim to predict stress and stress related phenomenon such as heave/subsidence or failure in natural conditions or under oil and gas or aquifer development conditions.
Subsurface models are often generated using geo-statistical methods. Such models often include high level, discrete parameters which are variables that condition/control a number of lower order continuous parameters/variables. Discrete high level variables are typically used in subsurface modelling to capture geological heterogeneities of critical importance to the overall process. Discrete geological 3D parameters (e.g. facies, architectural elements) often display complex 3D relationships.
A geobody is a group of cells having similar properties which indicate the presence of a particular fluid phase. Typically they have been identified or extracted by comparing, on an individual cell basis, the relevant cell property or properties to a threshold.
However, the present methods have a number of drawbacks. The core method does not necessarily favour contiguous groups of cells, and separate non-contiguous groups may be identified as part of the geobody based upon the threshold comparison. Present methods also cannot ensure that a volume criteria is reached without performing the entire method and calculating the resultant volume. Should the volume be insufficient, the method needs to be performed again with new thresholds.
It would be desirable to provide for an improved method of geobody extraction.